As an in-vehicle display apparatus, an apparatus for displaying a display window of an external terminal device is well known. An apparatus disclosed in patent literature 1 is one example of the above-described in-vehicle display apparatus. The in-vehicle display apparatus disclosed in patent literature 1 displays a display window of a mobile terminal on an in-vehicle display section. Further, in patent literature 1, the in-vehicle display apparatus obtains display region information (i.e., display window size) of the mobile terminal, and compares the display region information of the mobile terminal with a display window size of the in-vehicle display section in order to decide a scale factor for converting the display window of the mobile terminal to a display window of the in-vehicle display section. Further, patent literature 1 discloses an example of a display mode, in which one or more display windows are converted by different scale factors. Patent literature 1 also discloses examples of display modes, in which the display window of the mobile terminal is displayed in a scale-down manner so that the display window of the mobile terminal is completely displayed on the in-vehicle display section or the display window of the mobile terminal is displayed in a scale-up manner. In a case where the display window of the mobile terminal is displayed in the scale-up manner, the display window of the mobile terminal fails to be completely displayed on the in-vehicle display section. Thus, patent literature 1 discloses that a scroll button is prepared in order to completely display the display window of the mobile terminal on the in-vehicle display section.
In patent literature 1, the display window of the mobile terminal is displayed on the in-vehicle display section by converting the entire display window of the mobile terminal by a predetermined horizontal to vertical scale factor. In patent literature 1, in order to display the entire display window of the mobile terminal on the in-vehicle display section, the entire display window of the mobile terminal is scaled down. Thus, the display window of the mobile terminal is difficult to be identified in detail in a short time. In order to easily identify the display window displayed on the in-vehicle display section in detail, the entire display window needs to be scaled up. However, when scaled up, the display window of the mobile terminal fails to be completely displayed on the in-vehicle display section at one time. Thus, the entire display window of the mobile terminal, which is displayed on the in-vehicle display section, cannot be confirmed without scrolling the display window on the in-vehicle display section.